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Davis, California

Tuesday, June 25, 2024

Column: Wild blue yonder

One of my favorite stories about scientific mystery involves a flock of pigeons. Pigeon poop, to be exact.

Back in 1964, two scientists named Arno Penzias and Robert Wilson were working in a New Jersey lab with a radio wave receiver. The huge receiver was shaped like a flared “horn,” and Penzias and Wilson hoped to use it to learn about the radiation emitted from stars and galaxies.

There was one problem. They could never get a clear sound from the receiver – there was always a faint hiss that wasn’t supposed to be there. They’d point the antennae at different points in the sky, but there was always a hiss. They thought maybe it came from nearby New York City, but that wasn’t it.

Penzias and Wilson knew there were some pigeons roosting in the horn. Ah ha! Pigeon poop could emit tiny amounts of radiation! But it wasn’t the poop.

“Poor Bob Wilson went in there and cleaned it out,” said Anthony Tyson, a professor of physics at UC Davis.

Tyson was working in that New Jersey lab when Penzias and Wilson detected the “hiss” of radiation. He was there when the two astronomers agonized over the mysterious noise.

“They threw their hands up and couldn’t figure it out,” Tyson said.

Meanwhile, just 25 miles away, scientists at Princeton were working on a theory. They thought maybe there was radiation left over from the burst of energy we call the Big Bang. This “background” radiation could have been ricocheting around since the birth of the universe.

If only they had a receiver strong enough to pick it up.

It took just one phone call between the labs for the Princeton folks to figure out what was going on with the mysterious hiss. It was what we now call “cosmic microwave background radiation.”

What started as annoying background noise was really a breakthrough. Scientists today will tell you that the universe is expanding. One reason they know this is because the energy in this background radiation is constantly spreading out to fill the newly available space.

Wilson and Penzias won the Nobel Prize in Physics in 1978, and their pigeon trap is now owned by the Smithsonian.

I love this story because it shows how we can never know what we don’t know. It sounds obvious. It sounds stupid. But while scientists are often pictured with charts and facts and figures, they also have to leave room for mystery.

Put simply, science is about asking “what is that?”

For cosmologists who came after Penzias and Wilson, the big question is dark matter.

Dark matter screws with gravity. We can’t see it, but it’s probably there. When scientists look at galaxies, they can see stars and planets pulled toward unseen objects, causing what Tyson called a “tell-tale distortion.”

It doesn’t make sense. The universal law of gravity shows that smaller particles are pulled toward more massive particles. So how can this mysterious matter be massive but invisible? By mass, there is actually more dark matter in our galaxy than stars or planets.

“Our galaxy is being held together by this energy,” Tyson said.

Then again, Tyson said, there might be no dark matter at all. Galaxies could be held together by “some funny kind of gravity” we haven’t figured out yet.

Tyson is currently working on the Large Synoptic Survey Telescope (LSST), a telescope that will take a picture of the sky every 15 seconds for 10 years.

The great thing about the LSST is that the scientists are expecting to be surprised. Somewhere in the pictures, there might be something confusing – the equivalent of Penzias and Wilson’s mysterious hiss. We’ll have more questions, more experimentation and maybe more answers.

Dark matter and background radiation have been bouncing around the universe for at least 13 billion years – ever since the Big Bang. We don’t know what else is out there.

“This is a gift from nature – the fact that we can actually look back billions of years,” Tyson said.

The trick is figuring out what to look for.

MADELINE McCURRY-SCHMIDT once got pooped on by a bird during a first date, so she understands why Penzias and Wilson were frustrated by those pigeons. Stupid birds. E-mail her at memschmidt@ucdavis.edu.


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